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HOW TO PREPARE: Dam Failure Inundation Hazard Map for Morgan Hill

NOTE: If multiple reservoirs are listed in the legend under one color, this indicates that the area shown with that color will be inundated if ANY of those reservoirs fail. It does NOT indicate that all of the reservoirs must fail at the same time in order to inundate the area.

Please be aware of the following information:

  • The maps were developed by dam owners to fulfill state law requirements. The maps are intended for emergency planning purposes.
  • The maps were developed using engineering hydrology principals and represent the best estimate of where the water would flow if the dam completely failed with a full reservoir. The inundation pathway is based on completely emptying the reservoir and does not include run-off from storms.
  • Many of the maps were developed in the 1970's. Should the maps have been developed more recently, different assumptions and map-making methods would have been used.

Copies of inundation maps for individual dams may be purchased from the California Department of Water Resources, Micrographics Department. Their phone number is (916) 653-6537.

This information was gathered from the the Association of Bay Area Governments web site.

Where the Water will Flow

The following is with the understanding that Anderson Reservoir would be 100% full and that there would be a 100% failure of the dam:

Inundation path for Anderson is down 101 & Monterey Highway, depths up to 26 feet. All Morgan Hill fire stations entirely submerged

  • North to Milpitas past the county line, past Montague Expressway. About 40 minutes to reach Martin Murphy School in San Jose -- depths still to 25 feet.
  • South to Gilroy just past the county line. Morgan Hill, San Martin and Gilroy City Centers entirely submerged.
    • 38 minutes to Watsonville Road
    • 42 minutes to Middle Road
    • 1 hour to San Martin, depth about 10 feet.
  • East just past Hill Road.
  • West just past De Witt.

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